Abstract: A liquid level monitoring system for underground storage tanks includes a submersible monitoring pipe system having telescoping sections that are biased to an extended position enabling the pipe to be self-retained within the tank between its upper and lower walls adjacent to and offset axially from a selected access opening in the tank, such as the discharge opening which normally accommodates the pump for the tank. The pipe system houses an electronic level sensor which is coupled to an above ground control system via conductor wires. An elongate accessing member having an openable and closable clamp jaw assembly for gripping the pipe system and disposing it in a compressed condition within the tank offset from the riser opening is provided as a part of the system.

Abstract: A liquid level monitoring system for underground storage tanks includes a submersible monitoring pipe having telescoping sections that are spring biased to an extended position enabling the pipe to be self-mounted within the tank between its upper and lower walls adjacent to and offset axially from a selected axis opening in the tank, such as the discharge opening which normally accommodates the pump for the tank. The pipe houses an electronic level sensor which is coupled to an above ground control system via conductor wires. A tank adapter is secured to the tank opening and provided with a passage through which the conductor wires extend for routing out of the tank without interfering with the clearance normally provided for insertion and removal of the pump.

Abstract: A method and system for detecting a leak in a high vapor-evolving hydrocarbon liquid underground storage tank filled incompletely with the liquid, wherein there is a projecting fill pipe connected with the ullage which is filled with hydrocarbon vapor and air. A vacuum source is connected to the fill pipe for withdrawing the atmosphere of the ullage and imposing a prescribed negative pressure. While some of the drawn off vapor and much of the air is exhausted to atmosphere, a significant portion of the ullage content is recirculated to build the relative proportion of hydrocarbon vapor to air in the ullage. The ullage is then isolated from the vacuum source and atmosphere, and allowed to stabilize over a predetermined time period with a reduced rate of hydrocarbon vapor release into the ullage.